Candida albicans is the most commonly occurring opportunistic fungal pathogen in humans. It has recently been shown that when estrogens are applied to cultures of C. albicans, the cells undergo a morphological change to the more infectious form of the organism. Based on thislead, an estrogen-binding protein from C. albicans has been isolated and cloned by a group at Stanford. The protein shows 46% sequence identity to a flavin-containing redox protein from Saccharomyces cerevisiae that has been studied for some years, but for which the function is still not known. We have begun a collaboration to characterize the scope of catalytic activity, redox properties and ligand binding behavior of this protein from C. albicans, with the eventual goal of defining its true function and possible relationship to infectivity. We are currently receiving protein from our collaborators at Stanford that has been expressed as a fusion protein in E. coli and proteolytically clipped after purification. In order to compare the properties of this recombinant protein with wild type protein, we have purified enzyme from a constitutively expressing strain of Candida and have shown it to have similar activity and molecular weight properties. Before proceeding with detailed characterization, we would like to determine whether the "wild type" protein we have isolated is indeed the same as the recombinant. In addition, there are at least two similar genes for the homologous protein in Saccharomyces and our collaborators have indicated that they have also cloned a second gene in Candida. Thus, we may have a misture of isozymes in the purified sample. At this point we would like to determine whether we have isolated a single protein or a mixture of isozymes. Then in addition, we want to obtain and compare sequence data for both recombinant and "wild type" proteins to verify that we have isolated the correct protein.